Question

我正在尝试在特定索引之后改组数组，我使用了拆分/联合机制，但是有什么有效的方法吗？

例如：

var arr = [0,1,2,3,4,5,6,7,8,9]


arr.shuffle(after index:4)
print(arr) -> //[0,1,2,3,4,7,9,8,6]

arr.shuffle(after index:0)
print(arr) -> //[0,3,2,1,4,9,8,6,8]

Answer 1

shuffle()是MutableCollection协议的一种方法，因此可以将其应用于数组 slice。示例：

var arr = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
arr[5...].shuffle() // Shuffle elements from index 5 to the end
print(arr) // [0, 1, 2, 3, 4, 6, 8, 7, 5, 9]

Answer 2

extension Array {
    mutating func shuffle(fromIndex:Int) {
        self[fromIndex...].shuffle()
    }

    func shuffled(fromIndex:Int) -> [Element]{
        return self[..<fromIndex] + self[fromIndex...].shuffled()
    }
}

var arr = [0,1,2,3,4,5,6,7,8,9]
arr.shuffle(fromIndex: 4) // 0,1,2,3,x,x,x,x,x,x - x - any of the value of 4...9

let arr2 = [0,1,2,3,4,5,6,7,8,9]
var arr3 = arr2.shuffled(fromIndex: 4)

要使mutating func shuffle(fromIndex:Int)工作，数组必须为var。这不适用于let。 func shuffled(fromIndex:Int) -> [Any]-用于随机组合的let数组

索引后随机排列数组

2 个答案: